The present invention generally relates to dental restorative or corrective work. In particular, the present invention relates to an apparatus for measuring, recording and analyzing mandibular movement for use in dental restorative and corrective work.
In restorative dentistry, it is critical that proper occlusion between the upper and lower jaws of a patient be established to maximize comfort of the patient during mastication. In corrective dentistry, especially that concerning those suffering from tempormandibular joint syndrome, a full and complete understanding of a specific patient's jaw movement is needed in order to properly diagnose and implement a treatment plan for the patient. Improper occlusion may not only lead to the discomfort of the patient while chewing, but may also contribute to other chronic debilitating affects, including improperly aligned condyles. Because such occlusion of the upper and lower teeth is so closely related to condylar movement about the tempormandibular joint, a complete understanding of such movement is essential in making gnathological determination factors related to the dental restorative or corrective work.
Occlusal motion is quite complex. While a dominant factor of occlusal motion includes pivotal movement of the lower jaw about a hinge axis through the TMJ, other factors contributing to the movement include torsional and linear movement of the lower jaw. Such movement can be characterized as having factors relating to pitch, yaw and roll, as well as linear movement transverse to the condylar axis. It has therefore been quite difficult to not only record mandibular movement, but also precisely replicating such movement within precise tolerances.
There exist in the art a wide variety of devices which have attempted to record mandibular movement. Perusing the prior art, incremental changes in the attempts to record such mandibular movement can be observed. Early examples include dental pantographs, such as those suggested by U.S. Pat. No. 1,033,562 and U.S. Pat. No. 2,794,253. These pantographs had several inherent shortcomings, including ease of use, discomfort when applied to the patient and overall accuracy of recording. Other examples of dental pantographs include: U.S. Pat. No. 3,218,716; U.S. Pat. Nos. 3,431,649; and 4,034,475. Briefly, using such pantographic recording systems, dentists attach mechanical devices, or clutches, to the upper jaw and the lower jaw of patient. This system of clutches allowed the dentist to attach a network of connecting bars and linkages to the upper and lower jaws of the patient. Each clutch is filled with a compound material which forms a surface around the teeth of the patient, then a cement is used to temporally attach the clutch thereto. Each clutch is in turn operatively linked to a pantograph such that the dentist can guide the jaws and record the resulting movement pattern. Using a stylus and magnetic pads to record the movements of the jaw, a set of tracings in the form of trajectories were obtained.
The resulting tracings have the appearance of a regular strip charge recorder with no interface to any data storage device for future analysis. Despite the accuracy of the aforementioned pantographic systems, the overall time required to prepare the system with the patient and the overall difficulty in using the pantographic system has hindered its wide-spread growth. Subsequently, less accurate but more workable systems are have become more popular.
More recently, there have been other attempts to record mandibular movement. One such attempt includes supplementing the recording surface of the aforementioned dental pantographs with pressure sensitive elements capable of transmitting an electric signal. Such devices, however, still did not accurately and precisely depict three-dimensional motion of the jaw.
Another example includes the use of corresponding arrays of ultrasonic transmitters and receivers in order to record jaw movement with at least six degrees of the freedom. This attempt again required the patient to wear the entire device in order to record movement of the lower jaw. Also, this attempt has inherent accuracy and precision issues as the contact points for the arrays within each jaw are secluded to a single area which, for example, can compound errors when determining roll characteristics of mandibular movement.
An even further example includes the use of video cameras to optically capture a target image attached to a tooth on the upper jaw and a target image attached to a tooth on the lower jaw of the patient. This attempt also has inherent accuracy and precision issues as the contact points within each jaw are secluded to movement of the lower jaw about a single tooth, which may not accurately or precisely record roll or uneven pivoting about the condyles.